Healthy seedings of uniform size are required for transplanting in order to produce a superior plant in a greenhouse or in the filed. Many materials, cell/edge/sidewall shapes and sizes of plant growth containers or trays are commercially available for plant or seedling culture varying in price, design and durability. A major problem associated with a conventional tray is root binding or tangling which deters plant root development within the container and after the seedlings are transplanted. An example of the air-pruning tray and its important application as an integral part of the fully automatic transplanting have been disclosed by Dr. Barney K. Huang in U.S. Pat. Nos. 3,712,252 and 3,446,164.
Numerous field tests indicate that the air-pruned cuttings and seedlings are significantly superior in growth performance both in the trays and after transplanting and that effective fully automatic transplanting can be performed with the air-pruned seedlings for various crops. However, the mass production of an integrated air-pruning tray and detachable screen bottom at a low cost has been a problem due to conventional plastic forming processes.